Actually, $4 is fairly moderate by Market standards...Take a look at SPB Shell, if you want to see an overpriced launcher. $15 for that piece of junk is absolutely murderous! I understand that $4US carries a different value throughout the world, and what may be expensive to some, will seem cheap to others. Unfortunately, there's no solution, since devs don't have the ability to adjust price by country or region.
As for Nova, I believe the stock launcher is under the Apache license, and therefore, is not open source. As such, no launchers written off of stock code, need to be open. Someone please correct me if I'm wrong, but I think Kevin addressed this topic at some point a while ago, and I think this was the gist of his response.
Sent from my DROID3 using xda premium